Duct Collection System
Duct Collection System
(OP)
Hi, Im looking at designing a new Dust Colleciton System, with an extract fan, turrit dust collecor unit and circular ductwork to 4 machine outlets points, approx 4" per outlet.
I want to make it as efficient as possible.
Not all machines will be operational at once. I would like to put the fan motor on a VFD but do I have to watch the minimum velocity in the ductwork?..... so am I allowed to ramp down the fan if some rooms are not working and their dampers are closed? Are you allowed to close the dampers if you want to maintain min velocity in the duct????
Should I put velocity sensors at each outlet and make and automatic open./close damper for each machine? What velocity or pressure drop/length shoud I be sizing my duct on?
I have never before done one of these but I work in a site with many of theese systems that are over 20 years old, big motors (90kW) and in some instances only one machine hooked up and the rest dampered off beacuse of noise issues and not needed etc...
I would really appreciate your help..... any pointers anyone?
I want to make it as efficient as possible.
Not all machines will be operational at once. I would like to put the fan motor on a VFD but do I have to watch the minimum velocity in the ductwork?..... so am I allowed to ramp down the fan if some rooms are not working and their dampers are closed? Are you allowed to close the dampers if you want to maintain min velocity in the duct????
Should I put velocity sensors at each outlet and make and automatic open./close damper for each machine? What velocity or pressure drop/length shoud I be sizing my duct on?
I have never before done one of these but I work in a site with many of theese systems that are over 20 years old, big motors (90kW) and in some instances only one machine hooked up and the rest dampered off beacuse of noise issues and not needed etc...
I would really appreciate your help..... any pointers anyone?





RE: Duct Collection System
The primary method of sizing ducting serving a dust collection system is to maintain a certain minimum velocity through the duct. This velocity will allow the particles to be suspended in the air and it will also allow the particles to be transported to the collector.
The minimum velocity that you size your duct will depend on the size of your particles. For woodworking and other light particles (not metals), 3,500 to 4,000 FPM is typically used.
I would suggest you run different scenarios. (1) Machine on, (2) Machines on, (3) Machines on and (4) Machines on. Then determine what the velocities would be in the duct and the total pressure drops, in order to get a better understanding of how to size your ducting and fan.
A VFD would be beneficial in being able to control fan air flow and velocities. I think it is a good idea.
Justin K, P.E.
http://www.engproguides.com
RE: Duct Collection System
RE: Duct Collection System
B.E.
The good engineer does not need to memorize every formula; he just needs to know where he can find them when he needs them. Old professor
RE: Duct Collection System
RE: Duct Collection System